1. Field of the Invention
This invention concerns an exhaust system for outboard engines, in particular the structure of the muffler which comprises the exhaust system.
2. Background of Prior Art
Exhaust systems for outboard engines are typically constructed such that exhaust gases emitted from the engine are first expanded in an expansion chamber and then expelled to outside the engine. Normally, this expansion chamber is a long, narrow cylindrical muffler which is contained in an upper housing of the engine and associated propulsion system.
However, the upper housing of an outboard motor propulsion unit has a variable length depending upon the application for which the engine was designed, the type of engine and its specifications. This requires a variable length muffler for accommodating various types (i.e., lengths) of upper housings.
Mufflers for such engines, however, are normally formed by die casting or other metal casting methods, so separate molds are required to make mufflers of different lengths. Also, since mufflers are relatively long objects, these molds can be quite large. Thus, having to prepare large molds for each muffler having a different length in the prior art was a big factor in increased costs.